<!--
 * @Descripttion: 
 * @version: 
 * @Author: wtzhang
 * @Date: 2021-09-24 14:36:02
 * @LastEditors: wtzhang
 * @LastEditTime: 2021-09-24 14:40:12
-->
<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<style>
.content {
  width: 80%;
  height: 1400px;
  margin: 0 auto;
  background-color: antiquewhite;
}
.top {
  position: fixed;
  left: 50%;
  margin-left: 40%;
  top: 12%;
  width: 50px;
  height: 100px;
  background-color: skyblue;
}
</style>
<body>
  <div class="content">版心区域</div>
  <div class="top">固定盒子</div>
</body>
</html>